The specific aims of this proposal are first to modify the current procedures of purifying murine colony-stimulating factor (CSF-1) by using an immunoadsorbent affinity chromatography. Affinity column will be prepared by attaching purified monoclonal antibody against CSF-1 to Sepharose 4B. We will use this affinity column for the large-scale purification of CSF-1. We will also use a membrane preparation derived from peritoneal exudate cells or J774 cells to study its binding and interaction with CSF-1. Preliminary studies on the mechanism of action of CSF-1 will be performed. We will determine whether CSF-1 binding enhances protein phosphorylation and will identify the phosphorylated components. The second portion of this proposal involves the preparation of monoclonal antibodies against receptor for CSF-1. Using a fluorescence-activated cell sorter (FACS) and anti-CSF receptor antibody, we plan to isolate a subclass of mononuclear phagocytes possessing CSF-1-receptor present in alveolar spaces and peritoneal cavity. Following separation, these two cell populations (CSF-1 receptor positive and -negative) will be characterized and compared for their morphology, enzyme staining, colony-forming ability and secretion of plasminogen activator (PA). The effect of CSF-1 on these two cell populations will also be studied.